The Neuroepidemiology Branch and an international group of expert and nonexpert neurologists evaluated the accuracy in the diagnosis of different Parkinsonian and dementia disorders, including the accuracy of published criteria for the clinical diagnosis of progressive supranuclear palsy (PSP), using clinical material confirmed by postmortem examination. The Neuroepidemiology Branch, the Society for Progressive Supranuclear Palsy, Inc. (SPSP), and an international group of expert neurologists, used the previously described data to develop better clinical criteria for the diagnosis of PSP. Vascular dementia is the second most common cause of dementia in the elderly. Analytic studies to determine risk factors for vascular dementia and Alzheimer's disease are being planned to be developed in Argentina in a well-defined population. Although diagnostic accuracy is important in epidemiologic studies, most case-control studies on dementia do not have well-defined populations. Neuroradiological anatomic (MRI) and perfusion imaging (Tc99 HMPAO cerebral SPECT) studies useful to differentiate Alzheimer's disease dementia from vascular dementia will be used in our studies.